Touch sensing technology capable of providing a natural interface between an electronic system and user has found widespread applications in a variety of fields, for example, in mobile phones, personal digital assistants (PDAs), automatic teller machines (ATMs), game machines, medical devices, liquid crystal display (LCD) devices, light emitting diode (LED) devices, plasma display panel (PDP) devices, computing devices, and the like, where a user may input desired information and/or operate the electronic system through a touch sensing device associated with the electronic system.
Recently, an LCD incorporating touch function has been developed. Those touch functions senses the pressure or capacitance difference caused by a touch of a finger or a stylus and provide electrical signals corresponding thereto for the LCD. The external device determines whether and where a touch exists on a display panel of the LCD based on the processed electrical signals and may return image signals to the LCD, which are generated based on the information. Although the touch function may be provided on an external device such as a touch screen panel to be attached to the LCD, it may increase the thickness, the weight and the additional cost of the LCD. A photosensor incorporated into an LCD may be implemented as a TFT disposed in a pixel displaying an image. However, such a photosensor causes many errors in photosensing responsive to touch since an output characteristic of the photosensor varies with ambient circumstances, i.e., an intensity of ambient light, a luminance of a backlight, temperature, and so on. Accordingly, the LCD device may perceive no touch although a touch has occurred or may perceive a touch although no touch has occurred.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.